Why Is My Infant Refusing Formula Milk Despite Changing Brands And Being Mixed-fed?

Hi my daughter is 4 months old . For the last 2 months she is not drinking milk through breasts so I am mix feeding her with my pumped milk And formula by bottle. . But now for the last one week she is resisting formula . I changed formula from lactogen to enfamil but no use . Why is shw doing so ?.